Generally, an auxiliary steering device is used as a device configured to ensure steering stability of a vehicle and assist with separate power. In such an auxiliary steering device, a device using a hydraulic pressure has been typically used, but recently, an electric steering device having a low power loss and superior accuracy is used.
The electric steering device drives a motor by an electronic control device according to a driving condition and manipulation information of a driver, which are detected by a vehicle speed sensor, a torque sensor, an angle sensor, and the like, to ensure turning stability and promptly provide a restoring force, thereby allowing the driver to safely drive.
The vehicle speed sensor is a device configured to sense a running speed of a vehicle that is driving, the torque sensor is a device configured to sense a torque applied to a steering shaft and output an electric signal proportional to the sensed torque, and the angle sensor is a device configured to output an electric signal proportional to a rotational angle of the steering shaft.
Recently, a torque angle sensor is proposed as a device configured with a single sensor in which the torque sensor and the angle sensor among these sensors are integrated to sense steering handle manipulation information of a user, and the use thereof is increasing.
FIG. 1 is an exploded perspective view illustrating such a conventional torque angle sensor.
The torque angle sensor is configured with an upper case 100, a rotor 500, a stator 600, a printed circuit board (PCB) 400, a main gear 410, a sub-gear 420, and a lower case from a top to a bottom of the torque angle sensor module.
The rotor 500 and the stator 600, which serve a sensing function of the torque sensor, are disposed at an upper side based on the PCB 400, and the gears 410 and 420 serving as the angle sensor are disposed at a lower side based on the PCB 400.
In the case of the torque sensor, magnets are disposed along an outer circumferential surface of the rotor 500, and the stator 600 having protruding pieces corresponding to polarities of the magnets is disposed at an outer circumferential surface of the magnets such that the torque sensor detects a torque of each of a input shaft and an output shaft by detecting a magnetic amount according to a difference in rotation amount between the rotor 500 and the stator 600 and transmits the detected torque to an electronic control device.
In the case of the angle sensor, as a driver rotates a steering handle, the main gear 410 attached to a steering shaft rotates in synchronization with the rotation of the steering handle and thus a difference in rotational angle is generated, and, at this point, Hall integrated circuits (ICs) 401 and 402 recognize magnetic field and rotational direction of the magnets attached to sub-gears 420 that are attached to the main gear 410 such that the angle sensor transmits a signal to the electronic control device.
However, since a backlash (a gap between a pair of gears) is generated due to an engagement structure between the main gear and the sub-gears, there is a problem for the angle sensor in that an accurate measurement of a steering angle is very difficult.
In addition, there causes a problem in that an assembling man-hour and a defect rate are increased during assembly due to a large number of components, and there is a problem of increasing cost due to the large number of components, and specifically, since two or more Hall ICs with relatively high prices should be configured, an increase of manufacturing costs is caused.